import { NextRequest, NextResponse } from 'next/server'
import { auth } from '@/auth'
import { prisma } from '@/lib/prisma'
import { revalidatePath } from 'next/cache'

function parseDate(v: unknown): Date | null {
  if (!v) return null
  const d = new Date(v as string)
  return isNaN(d.getTime()) ? null : d
}

export async function POST(req: NextRequest) {
  try {
    const session = await auth()
    if (!session?.user?.id) {
      return NextResponse.json({ success: false, error: 'Unauthorized' }, { status: 401 })
    }

    const userId = session.user.id
    const formData = await req.formData()
    const file = formData.get('file') as File

    if (!file) {
      return NextResponse.json({ success: false, error: 'No file provided' }, { status: 400 })
    }

    const text = await file.text()
    let importData: any

    try {
      importData = JSON.parse(text)
    } catch {
      return NextResponse.json({ success: false, error: 'Invalid JSON file' }, { status: 400 })
    }

    if (!importData.data || !importData.data.notes) {
      return NextResponse.json({ success: false, error: 'Invalid import format' }, { status: 400 })
    }

    const stats = { notes: 0, labels: 0, notebooks: 0, skipped: 0 }

    // 1. Notebooks — parents first, preserve original IDs
    if (importData.data.notebooks?.length) {
      const sorted = [...importData.data.notebooks].sort((a: any, b: any) => {
        if (!a.parentId && b.parentId) return -1
        if (a.parentId && !b.parentId) return 1
        return 0
      })

      for (const nb of sorted) {
        try {
          await prisma.notebook.upsert({
            where: { id: nb.id },
            update: {
              name: nb.name,
              icon: nb.icon ?? null,
              color: nb.color ?? null,
              order: nb.order ?? 0,
              parentId: nb.parentId ?? null,
              trashedAt: parseDate(nb.trashedAt),
              updatedAt: new Date(),
            },
            create: {
              id: nb.id,
              name: nb.name,
              icon: nb.icon ?? null,
              color: nb.color ?? null,
              order: nb.order ?? 0,
              parentId: nb.parentId ?? null,
              trashedAt: parseDate(nb.trashedAt),
              userId,
              createdAt: parseDate(nb.createdAt) ?? new Date(),
              updatedAt: parseDate(nb.updatedAt) ?? new Date(),
            },
          })
          stats.notebooks++
        } catch (e: any) {
          if (e.code === 'P2002') {
            // unique constraint — try with new ID
            const parentId = nb.parentId ?? null
            await prisma.notebook.create({
              data: {
                name: nb.name,
                icon: nb.icon ?? null,
                color: nb.color ?? null,
                order: nb.order ?? 0,
                parentId,
                trashedAt: parseDate(nb.trashedAt),
                userId,
                createdAt: parseDate(nb.createdAt) ?? new Date(),
                updatedAt: parseDate(nb.updatedAt) ?? new Date(),
              },
            })
            stats.notebooks++
          } else {
            stats.skipped++
          }
        }
      }
    }

    // 2. Labels — preserve original IDs
    if (importData.data.labels?.length) {
      for (const lb of importData.data.labels) {
        try {
          await prisma.label.upsert({
            where: { id: lb.id },
            update: {
              name: lb.name,
              color: lb.color ?? null,
              notebookId: lb.notebookId ?? null,
              type: lb.type ?? 'user',
            },
            create: {
              id: lb.id,
              name: lb.name,
              color: lb.color ?? null,
              notebookId: lb.notebookId ?? null,
              type: lb.type ?? 'user',
              userId,
              createdAt: parseDate(lb.createdAt) ?? new Date(),
              updatedAt: parseDate(lb.updatedAt) ?? new Date(),
            },
          })
          stats.labels++
        } catch {
          stats.skipped++
        }
      }
    }

    // 3. Notes — preserve original IDs
    if (importData.data.notes?.length) {
      for (const n of importData.data.notes) {
        try {
          const labelIds: string[] = n.labelIds || []
          const validLabelIds = labelIds.length
            ? await prisma.label.findMany({
                where: { id: { in: labelIds }, userId },
                select: { id: true },
              }).then(ls => ls.map(l => l.id))
            : []

          await prisma.note.upsert({
            where: { id: n.id },
            update: {
              title: n.title || 'Untitled',
              content: n.content || '',
              color: n.color || 'default',
              isPinned: n.isPinned ?? false,
              isArchived: n.isArchived ?? false,
              type: n.type || 'richtext',
              order: n.order ?? 0,
              isMarkdown: n.isMarkdown ?? false,
              size: n.size || 'small',
              autoGenerated: n.autoGenerated ?? false,
              historyEnabled: n.historyEnabled ?? true,
              checkItems: n.checkItems ?? undefined,
              images: n.images ?? undefined,
              links: n.links ?? undefined,
              trashedAt: parseDate(n.trashedAt),
              notebookId: n.notebookId ?? null,
              contentUpdatedAt: parseDate(n.contentUpdatedAt),
              updatedAt: new Date(),
              labelRelations: {
                set: validLabelIds.map(id => ({ id })),
              },
            },
            create: {
              id: n.id,
              title: n.title || 'Untitled',
              content: n.content || '',
              color: n.color || 'default',
              isPinned: n.isPinned ?? false,
              isArchived: n.isArchived ?? false,
              type: n.type || 'richtext',
              order: n.order ?? 0,
              isMarkdown: n.isMarkdown ?? false,
              size: n.size || 'small',
              autoGenerated: n.autoGenerated ?? false,
              historyEnabled: n.historyEnabled ?? true,
              checkItems: n.checkItems ?? undefined,
              images: n.images ?? undefined,
              links: n.links ?? undefined,
              trashedAt: parseDate(n.trashedAt),
              notebookId: n.notebookId ?? null,
              userId,
              createdAt: parseDate(n.createdAt) ?? new Date(),
              updatedAt: parseDate(n.updatedAt) ?? new Date(),
              contentUpdatedAt: parseDate(n.contentUpdatedAt),
              labelRelations: {
                connect: validLabelIds.map(id => ({ id })),
              },
            },
          })
          stats.notes++
        } catch (e: any) {
          if (e.code === 'P2002') {
            await prisma.note.create({
              data: {
                title: n.title || 'Untitled',
                content: n.content || '',
                color: n.color || 'default',
                isPinned: n.isPinned ?? false,
                isArchived: n.isArchived ?? false,
                type: n.type || 'richtext',
                order: n.order ?? 0,
                isMarkdown: n.isMarkdown ?? false,
                size: n.size || 'small',
                notebookId: n.notebookId ?? null,
                userId,
                createdAt: parseDate(n.createdAt) ?? new Date(),
                updatedAt: parseDate(n.updatedAt) ?? new Date(),
                contentUpdatedAt: parseDate(n.contentUpdatedAt),
              },
            })
            stats.notes++
          } else {
            stats.skipped++
          }
        }
      }
    }

    revalidatePath('/home')
    revalidatePath('/settings/data')

    return NextResponse.json({ success: true, ...stats })
  } catch (error) {
    console.error('Import error:', error)
    return NextResponse.json({ success: false, error: 'Failed to import notes' }, { status: 500 })
  }
}